The present invention relates generally to special reproducing systems in apparatuses for reproducing rotary recording mediums and more particularly to a special reproducing system in an apparatus for reproducing by means of a reproducing transducer a video signal from a rotary recording medium on which the signal has been previously recorded along a spiral track, which system can shift the reproducing transducer to an adjacent track and accomplish a special reproduction wherein the reproduced picture becomes one of a motion differing to that of normal reproduction.
Known system for recording and reproducing information signals (such as video signals and/or audio signals) on and from disc-shaped, rotary mediums (referred to hereinafter simply as discs) are broadly divided into a system using optical reproduction, a system using a reproducing stylus employing a piezoelectric element, and a system utilizing variations in the elastrostatic capacitance between an electrode on the reproducing stylus and the recorded surface of the disc.
In accordance with a known electrostatic capacitance system, recording is accomplished by forming a spiral guide groove in the disc for guiding the reproducing stylus. At the same time, pits are formed in responsive correspondence with an information signal to be recorded on the bottom surface of the groove. In the reproducing system, the reproducing stylus is guided by the guide groove. The stylus traces the track within the groove and reproduces the signal in response to variations in the electrostatic capacitance.
In this known system, however, a reproducing stylus guiding groove is provided on the disc. The reproducing stylus is compulsorily guided by this guide groove. It is not possible for the reproducing stylus to undergo operations such as riding over the groove wall of one track, moving into another track and returning to the original track. If the reproducing stylus were to be forced to undergo such an operation, the groove and the stylus would be damaged. For this reason, it has not been possible in this known system to carry out special reproduction such as quick-motion picture reproduction, slow-motion picture reproduction, still-picture reproduction, and random access motion.
Accordingly, with the aim of overcoming the various problems of the known systems described above, a novel "Information signal recording and reproducing system" is disclosed in the specification of U.S. patent application Ser. No. 785,095, filed Apr. 6, 1977. According to this proposed system, the recording system forms pits in accordance with the information signal being recorded along a spiral track on a flat disc shaped recording medium, without forming a groove therein. In the reproducing system, a reproducing stylus traces over and along this track thereby to reproduce the recorded information signal in response to variations in the electrostatic capacitance.
In this system, since a groove for guiding the reproducing stylus is not provided on the disc, pilot or reference signals should be recorded on or in the vicinity of a track of the information signal, such as a video signal, on a rotary disc. At the time of reproducing, the reference signals are reproduced together with the video signal. Tracking servo control is carried out so that the reproducing stylus traces accurately along the track in response to the reproduced reference signals.
By the use of this previously proposed system, the recording track has no groove. There is no possibility whatsoever of the reproducing stylus or the recording medium being damaged. The stylus can trace the same portion of the track repeatedly many times, whereby a special reproduction such as still, slow motion, or quick motion reproduction becomes possible.